The present invention relates to a golf ball having a core and a cover of one layer or a plurality of layers. More particularly, the invention relates to a golf ball that contains water in the core composition and has a high rebound.
Various approaches are being taken to improve the flight performance and spin performance of golf balls. Golf balls generally have a construction that includes a core (solid center) encased by a cover of one layer or a plurality of layers. In recent years, the number of layers in this construction has increased. The core accounts for the majority of the ball in terms of volume, and so is thought to play a large role in determining the ball performance. Given that cores today are made of rubber compositions, numerous compounding studies are being done to improve the resilience of the core itself.
However, experimental data showing a relationship between differences in the rubber formulation and increased resilience are almost unknown, and much remains unclear about the mechanisms involved and the degree to which they contribute to resilience.
Several golf balls in which the ball properties were improved by focusing on hysteresis loss by the ball materials have been described in the art. For example, U.S. Pat. No. 8,469,835 (and the corresponding JP No. 4637762) discloses a golf ball having a thermoplastic polyurethane cover with a specific hysteresis loss. JP No. 3413800 discloses a golf ball composed of a center, a layer of rubber thread wound over the center, and a cover layer, with the rubber thread having a hysteresis loss under 0 to 100% extension at or below a given range. JP-A H08-294548 discloses a wound golf ball composed of a liquid center and a rubber thread layer, wherein the liquid center, when deformed to 50% of the center diameter, has a hysteresis loss at or below a given range.
Yet, the foregoing golf balls do not concern solid core materials. Also, additional improvements have been made recently to conventional core materials and core properties, and are expected to lead to still further increases in the rebound of golf balls.